My present invention relates to an aerial navigation system utilizing the Doppler effect. Such systems often make use of radio-navigational beacons installed on the ground and constituted by a plurality of dipoles arranged in a straight line or a circle, the dipoles being successively fed with high-frequency energy by switching circuits. These beacons simulate for the airplane a mobile emitter of radio waves executing a periodic motion.
The position of the airplane (elevation and/or azimuth) with respect to the beacons is often determined by counting the phase shifts introduced by the displacement of simulated mobile dipole from one end of the beacon to the other. This position determination is carried out with only limited precision, unless the beacons on the ground have such a large number of dipoles that their cost becomes prohibitive. Moreover, the installations become inoperative in the event any of the dipoles ceases to function so that the count obtained by the signal evaluation no longer has any significance.
In commonly owned U.S. Pat. No. 4,019,184, whose disclosure of which is incorporated herein by reference, I have disclosed a process and apparatus for the treatment of phase-modulated signals which are received aboard an airplane and, with the aid of one or more rotating disks in the path of a light beam modulated by these signals, are converted into a visual display. The disk speed is correlated with the motion of a ground-station aerial array comprising, for example, two dipoles each located at one end of an arm rotatable around an axis. The apparatus thus furnishes the pilot with a simultaneous visualization, in terms of elevation and azimuth, of the position of the airplane with respect to the beacon, while eliminating the effects of interfering signals reflected by obstacles.